Two or more intra AV nodal pathways in association with either a James or Kent extranodal bypass in 3 patients with paroxysmal supraventricular tachycardia.

In 3 patients studied using His bundle electrograms and programmed intracardiac stimulation, evidence has been obtained of thefunctioning of multiple A V nodal pathways in antegrade and retrograde directions during paroxysmal tachycardia due to an A V nodal reciprocating mechanism. In 2 patients extranodal bypasses as seen in the pre-excitation syndromes were shown to be present in addition to the intra A V nodal pathways. However, in one patient this extranodal bypass was not used in tachycardia and in the other it was concealed, only being brought to light when the tachycardia was terninated with intravenous verapamil. The significance of these findings is discussed.